Become a tactical ninja
Practise makes perfect, you have to put in lots of work to make all kinds of mates and tactics 2nd nature for you. Here on Chess.com the Tactics Trainer is an excellent tool but there are also plenty of other good tools around the net and I use many of them as well.
Check out this video to see how a FIDE Master trains his tactics. Note that this is just one exercise and I do many others. For more difficult tactics I like also doing them on a real board to train board vision.
Hope this video inspires you to work on your own chess and become a tactical ninja ;-)